1. Field of the Invention
The present invention relates to an improved top entry sub for use in drilling operations; specifically, to an apparatus of rated high tensile strength permitting the introduction of wireline or coiled tubing into the annulus of either a long and heavy string of drill pipe or of a drill string which can experience significant tensile loading from the movement of a drilling platform, such as by wave action, without disconnecting the sub from the drill string connected.
2. Background
Prior art devices include the U.S. Pat. No. Re. 33,150 to Boyd that discloses a side-entry sub that permits the connection within a drill string maintaining the drill string member above the tool to remain in axial alignment with the drill string member below the tool. This side entry sub has a longitudinal passage and a wireline passage, wherein the longitudinal axes of each intersect at an angle of about 6.5°. This device, while permitting significant tensile loading, does not permit the introduction of wireline tools into the annulus without disconnecting the drill string below the sub after the insertion of the wireline. A connection to the tubular string below this Boyd device must be disconnected and the wireline threaded through the side entry and thereafter connected to the longer wireline tools that make up the normal wireline assembly.
Other prior art devices include U.S. Pat. No. 5,284,210 to Helms that discloses a top-entry sub permitting the introduction of wireline Into the annulus of a drill string without the need to disconnect the sub from the well string. In the embodiment disclosed in FIGS. 1 and 4, the longitudinal axis of the drill pipe above and below the top-entry sub are substantially aligned. The Helms patent also discloses a wear sleeve for use with a double pin sub connected to the bottom of the top entry sub to avoid wear in the double pin sub by the wireline. The sleeve can be rotated periodically so the wear is more evenly distributed to increase the useful life of the sleeve.
Boyd also has an elongated wireline entry sub referred to as the Long Boy. This tool has a main passage portion extending from the lower end of the tool body to an upper point of the tool body. This main passage then extends into a principal passage that would be threaded onto a pipe or upper sub member so as to support the tool as it is positioned within the drill string above the rig floor. There is formed a second passage wherein a wireline extends therethrough downward into the main passage of the tool. The longitudinal axes of these three passages form a somewhat Y-shape. The angle between the axes of the main passage and the principal passage is about 2°. The angle between the axes of the main passage and the wireline passage is about 2.25°. Therefore, the total angle between the axes of the principal and wireline passages is about 4.25°.
U.S. Pat. No. 6,269,879 to Boyd discloses a wireline entry sub, like the Boyd Long Boy, but also having a wear resistant sleeve (Rockwell hardness of around 50) in the bottom end of the sub and/or in a sub saver attached to the bottom thereof. When worn by the wireline, the sleeve in the bottom of the wireline entry sub can be rotated by removing a screw so that fresh unworn surface can be used. The axes of the main passage (referred to therein as the principal passage), the principal passage (referred to therein as the first principal passage) and the wireline passage (referred to therein as the second passage) also form a Y-shape.
The embodiment disclosed in FIG. 3 of the Helms patent, the Boyd Long Boy, and the elongated wireline entry sub disclosed in U.S. Pat. No. 6,269,879, however, introduce a bending moment into the drill string because of the offset between the longitudinal axis of the drill string above the wireline entry sub with the longitudinal axis of the drill string below the sub. As more and more tension is placed on such tools as from the use of long strings of drill pipe on offshore floating platforms, which can drill in up to 10,000 feet of water, the alignment of the upper drill string member with the lower drill string members becomes critical. The bending moment can overstress the threads on the string and cause failure of the system.
Thus, there is a need to improve and provide such a wireline device that minimizes the bending moment of prior art devices, provides axial alignment of the wireline or coiled tubing pathway over the drill pipe annulus, and provides the entry of wireline or coiled tubing devices without having to disconnect the drill string therefrom.